1. Field of the Invention
The present invention relates to fluid-operated cylinders generally and, more particularly, but not by way of limitation, to a novel fluid-operated cylinder that provides both linear and rotary motion.
2. Background Art
A number of well-known operations require the provision of both rotary and linear motion. For example, the simple robotic placing of a screw in a threaded hole requires that linear motion be provided such that the screw can be advanced toward the hole and, when the end of the screw reaches the hole, the linear motion continues, while rotary motion is required to thread the screw into the hole. Many other such uses of both linear and rotary motion can be cited wherein the linear and rotary motion is sequential or consecutive or some combination thereof
Electromechanical devices that provide both linear and rotary motion are well known. An example of such a device is described in U.S. Pat. No. 3,407,680, issued Oct. 29, 1968, to Westmoreland, and titled RECIPROCATING POWER ARRANGEMENTS. Described therein is an electromagnetic linear/rotary device comprising two electric motors having a common shaft extending therethrough. One motor cooperates with a splined portion of the shaft such that rotary motion of the motor causes the shaft to rotate. The other motor cooperates with a threaded portion of the shaft such that rotary motion of the motor causes the shaft to advance axially one direction or the other depending on the direction of rotation of the motor. Linear, rotary, or both linear and rotary motion of the shaft is provided depending on whether both motors are operating and the speed at which one or both of the motors is operated. One or both ends of the shaft may be operatively attached to other elements.
Electromechanical devices have certain drawbacks, among which are the relatively complex control devices required and, if the electromechanical devices are used in a hazardous environment, special equipment must be employed to avoid explosions, etc.
Also well known are fluid-operated cylinders that typically employ a stationary cylinder having disposed therein a piston. Pressurized fluid, air or hydraulic oil, for example, is introduced into the cylinder on one side of the piston to drive the piston and a shaft attached thereto linearly in one direction. A workpiece, biasing means, and/or the introduction of pressurized fluid into the cylinder on the other side of the piston drives the piston and a shaft attached thereto in the other direction. Such an arrangement is simple, is easily controlled, and is relatively safe in hazardous environments. However, such a cylinder is deficient in that it does not provide rotary motion as well as linear motion.
Accordingly, it is a principal object of the present invention to provide a fluid-operated cylinder that provides both linear and rotary motion.
It is a further object of the invention to provide such a cylinder that lends itself well to robotic operations.
It is an additional object of the invention to provide such a cylinder that can be economically constructed using conventional techniques.
It is another object of the invention to provide such a cylinder that is single-acting.
It is yet a further object of the invention to provide such a cylinder that is double-acting.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.
The present invention achieves the above objects, among others, by providing, in a preferred embodiment, a fluid-operated cylinder to provide both linear and rotary motion to tooling, comprising: a cylindrical, rotatable member for attachment to rotatable means; a circular piston disposed in said cylindrical, rotatable member for back and forth axial motion in a cavity defined therein and rotatable by rotation of said cylindrical, rotatable member; a first port defined through said cylindrical rotatable member to introduce pressurized fluid into said cavity on a first side of said circular piston such as to cause said circular piston to move in a first direction; and a piston shaft fixedly attached to said circular piston and fixedly attachable to said tooling; whereby: when said rotatable member is rotated, rotary motion will be transmitted to said tooling by said piston shaft, and when said pressurized fluid is introduced into said cavity on said first side of said circular piston, said piston shaft will cause said tooling to move in said first direction.